Enzyme ptyalin acts on starch in the mouth. Ptyalin is an enzyme produced in the salivary glands in the mouth. When we eat foods containing starch, such as bread or potatoes, ptyalin helps to break down the starch into simpler sugars. This process begins in the mouth and continues in the stomach and small intestine, where other digestive enzymes and acids are added to further break down the food. The breakdown of food into smaller components is necessary for our bodies to absorb the nutrients and use them for energy.